This is based on the Implementation-Version attribute in the batik-util.jar (which is where this Version class lives) and the 'HeadURL' SVN keyword. The keyword be substituted with the URL of this file, which is then inspected to determine if this file was compiled from the trunk, a tag (a release version), or a branch. The format of the returned string will be one of the following:

Prior to release 1.7, the version string would be the straight tag (e.g. "batik-1_6") or the string "development.version". revision is the Subversion working copy's revision number.